Copper (Cu) plays key catalytic and regulatory functions for biochemical reactions that are critical to normal growth, development and health. Menkes disease and Wilson's disease are two severe human genetic disorders of Cu metabolism that result in childhood mortality and hepatic and neurological dysfunction, respectively. Inappropriate copper balance is linked to myeloneuropathy, prion disease, Alzheimer's and cardiovascular disease and cancer. Consequently, it is critical to understand the mechanisms by which cells control the acquisition, distribution and utilization of Cu. While the identify and functions of the Cu import, intracellular distribution and efflux machinery are beginning to be understood, we know very little about the physiological role of the Ctr2 protein, the regulation of Cu import and how organisms establish global Cu homeostasis. Three specific aims are outlined in this application, which are inter- related by the information they will decipher on the mechanisms of action of the mammalian Cu transport machinery and its regulation at the cellular and systemic level. In the first specific aim the physiological role of the mammalian Ctr2 protein in Cu acquisition will be ascertained through the analysis of mouse Ctr2 knock out mutants, through biochemical and cell biological experiments in cultured cells and through the analysis of Ctr2 mutant proteins. In the second specific aim the regulation of the Ctr1 Cu importer and the Ctr2 protein will be deciphered through an analysis of their post- translational regulation in cell culture. In the third specific aim experiments are outlined to identify a novel blood-borne signal that allows inter-organ communication between peripheral organs such as the heart and the copper acquisition and storage organs. Taken together, these investigations will decipher key functional roles and cellular and systemic regulatory mechanisms for the Cu acquisition machinery, the function of which is essential for normal growth, development and human health.